class_docstr: Base class for encoder neural module to be used in NLP models. 
code: def hidden_size(self) -> Optional[int]:
      raise NotImplementedError
  
file_path: NeMo/nemo/collections/asr/modules/transformer/encoder_module.py
imports: from abc import ABC
  from typing import Dict, Optional
  from nemo.core.classes import NeuralModule
  from nemo.core.neural_types import ChannelType, MaskType, NeuralType
label_desc: Use image node_id 3 for calling the EncoderModule obj's underlying member method code with example usage: obj.hidden_size() without return types